Nested Dictionaries

Jake Shoudy

Oct 19, 2022

CSCI110 - Lecture 25

Announcements

HW8

Big O Practice and Coding problems using Sets

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Can use dictionaries for coding problem 2 and 3.

Using just sets is extra credit

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Due TOMORROW at 11:59pm! (Oct 20th)

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Project 2: Part 2

More search engine things using 2D Lists :)

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Due Sunday October 30th at 11:59pm

Exam 2: Wednesday Oct 26

Topics (up until end of last week):

Binary <-> Base 10

Data types

Operators (arithmetic, comparison, logical)

Variables

if / elif / else

while loops

Strings (length, index, slice)

Functions

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Will include short answer & coding questions

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For Loops

Lists

2D Lists

Big O

Sets

Dictionaries

How to prepare:

• Review quizzes
• Review homeworks
• But also projects, labs, slides, replits

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Quiz 7

• Friday October 21st in the first 15 minutes of class
• Meet in lab
• Will cover:
• Big O
• Sets
• Dictionaries

Filters Hall of Fame!

- Adetoro Akinola

- Princess Nwanekwu

- Rupak Kunwar

- Michaela Robinson

- Keshav Shah

- Esther Ogundele

- Rohan Yadav

Recap

Tuples

• Immutable (therefore can be used as a key in a dictionary or in a set)
• Can still index, iterate, get length, etc.

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Tuples are similar to lists but the biggest distinction is...

player = (“xxCOOLGUYxx”, True, 25)

To create a tuple, we use parentheses instead of brackets:

Tuples as Keys

global_temps[(34.2384, -77.0118)]

global_temps = {

(38.8951, -77.0364): 74,

(32.1231, -71.3511): 61,

(34.2384, -77.0118): 55

}

55

Lists as Values of Dictionaries

songs = {

'Kendrick Lamar': ['N95', 'HUMBLE.'],

'Lizzo': ['Truth Hurts', 'Good As Hell'],

}

​

​

songs['Kendrick Lamar']

songs['Kendrick Lamar'][0]

songs['Kendrick Lamar'].append('Die Hard')

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['N95', 'HUMBLE.']

'N95'

Nested Dictionaries

Dictionaries

holidays = [

{'month': 10, 'day': 31},

{'month': 12, 'day': 25},

]

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{'month': 10, 'day': 31}

{'month': 12, 'day': 25}

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halloween = holidays[0]

christmas = holidays[1]

Dictionaries

holidays = [

{'month': 10, 'day': 31},

{'month': 12, 'day': 25},

]

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halloween = holidays[‘halloween’]

christmas = holidays[‘christmas’]

How to change holidays to be able to use ‘halloween’ and ‘christmas’ to index?

Nested Dictionaries

holidays = {

‘halloween’: {'month': 10, 'day': 31},

‘christmas’: {'month': 12, 'day': 25},

}

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halloween_date = holidays[‘halloween’]

christmas_date = holidays[‘christmas’]

{'month': 10, 'day': 31}

{'month': 12, 'day': 25}

​

Nested Dictionaries: Iteration

holidays = {

'halloween': {'month': 10, 'day': 31},

'christmas': {'month': 12, 'day': 25},

}

for holiday in holidays:

month = holidays[holiday]['month']

day = holidays[holiday]['day']

print(holiday + ' is on ' + str(month) + '/' + str(day))

List of Dictionaries

songs = [

{'title': 'Circles', 'artist': 'Post Malone', 'genre': 'Pop'},

{'title': 'Ransom', 'artist': 'Lil Teccae', 'genre': 'Hip Hop/Rap'},

{'title': 'BOP', 'artist': 'DaBaby', 'genre': 'Hip Hop/Rap'},

{'title': 'Truth Hurts', 'artist': 'Lizzo', 'genre': 'Pop'},

{'title': '223\'s', 'artist': 'YNW Melly', 'genre': 'Hip Hop/Rap'},

]

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print(songs[0]['artist'])

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'Post Malone'

Nested Dictionaries

songs = {

'Circles': {'artist': 'Post Malone', 'genre': 'Pop'},

'Ransom': {'artist': 'Lil Teccae', 'genre': 'Hip Hop/Rap'},

'BOP': {'artist': 'DaBaby', 'genre': 'Hip Hop/Rap'},

'Truth Hurts': {'artist': 'Lizzo', 'genre': 'Pop'},

'223\'s': {'artist': 'YNW Melly', 'genre': 'Hip Hop/Rap'},

}

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print(songs['Circles']['artist'])

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'Post Malone'

Nested Dictionaries and Lists

songs = {

'Post Malone': [

{'title': 'Circles', 'year': 2019},

{'title': 'Goodbyes', 'year': 2019},

],

'Lizzo': [

{'title': 'Truth Hurts', 'year': 2019},

{'title': 'Good As Hell', 'year': 2016},

],

}

songs['Lizzo'][1]['year']

Nested Dictionaries and Lists

songs = {

'Post Malone': [

{'title': 'Circles', 'year': 2019},

{'title': 'Goodbyes', 'year': 2019},

],

'Lizzo': [

{'title': 'Truth Hurts', 'year': 2019},

{'title': 'Good As Hell', 'year': 2016},

],

}

songs['Lizzo'][1]['year']

Nested Dictionaries and Lists

songs = {

'Post Malone': [

{'title': 'Circles', 'year': 2019},

{'title': 'Goodbyes', 'year': 2019},

],

'Lizzo': [

{'title': 'Truth Hurts', 'year': 2019},

{'title': 'Good As Hell', 'year': 2016},

],

}

songs['Lizzo'][1]['year']

Nested Dictionaries and Lists

songs = {

'Post Malone': [

{'title': 'Circles', 'year': 2019},

{'title': 'Goodbyes', 'year': 2019},

],

'Lizzo': [

{'title': 'Truth Hurts', 'year': 2019},

{'title': 'Good As Hell', 'year': 2016},

],

}

songs['Lizzo'][1]['year']

Nested Dictionaries and Lists

songs = {

'Post Malone': [

{'title': 'Circles', 'year': 2019},

{'title': 'Goodbyes', 'year': 2019},

],

'Lizzo': [

{'title': 'Truth Hurts', 'year': 2019},

{'title': 'Good As Hell', 'year': 2016},

],

}

songs['Lizzo'][1]['year']

Nested Dictionaries and Lists

songs = {

'Post Malone': [

{'title': 'Circles', 'year': 2019},

{'title': 'Goodbyes', 'year': 2019},

],

'Lizzo': [

{'title': 'Truth Hurts', 'year': 2019},

{'title': 'Good As Hell', 'year': 2016},

],

}

songs['Lizzo'][1]['year']

Nested Dictionaries

Whenever we use a dictionary as a value within our dictionary

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Generally useful for modeling hierarchical data

Example: City population

population = {

'North America': {

'United States': {

...

'Washington': {...}

'Tennessee': {

'Nashville': 692587,

'Memphis': 650910,

'Chatanooga': 181370,

...

},

},

'Mexico': {...},

...

},

'Africa': {...},

...

}

population[‘North America’][‘United States’]

[‘Tennessee’][‘Nashville’]

Let’s Code!

https://replit.com/team/csci110-01

Nested Dictionaries